Photoelectric Effect Having run a photoelectric experiment you find that 45 nm i
ID: 1383067 • Letter: P
Question
Photoelectric Effect
Having run a photoelectric experiment you find that 45 nm is the longest wavelength of radiation that can cause electron photoemission from the cathode.
edit: 591 nm is actually the longest wavelength radiation, in (b) the wavelength should be 111 nm, and in (d) the intensity of the light source should be 19 mW/cm2
(a) What is the work function of the cathode metal?
(b) If radiation with wavelength of 1 nm is incident on the same cathode, what will be the KE of the photo-emitted electronics?
(c) What is the stopping voltage?
(d) If the intensity of the light source in (b) is 9 mW/cm2, what will be the current flowing in the external circuit if all photo-emitted electrons are collected?
Explanation / Answer
a) Wo = h*c/lamada
= 6.625*10^-34*3*10^8/(45*10^-9)
= 4.417*10^-18 J
= 4.417*10^-18/(1.6*10^-19) eV
= 27.6 eV
b) Apply,
E = Wo + KE
==> KE = E - Wo
= h*c/lamda - Wo
= 6.625*10^-34*3*10^8/(1*10^-9)
= 198.75*10^-18 - 4.417*10^-18
= 194.333*10^-18 J
= 194.333*10^-18/(1.6*10^-19)
= 1214.6 eV
c) Wo = q*Vo
Vo = Wo/q
= 4.417*10^-18/(1.6*10^-19)
= 27.6 volts
d) Sorry, no idea